1. Field of the Invention
The present invention relates to a continuous shearing apparatus controlling a thickness uniformity of a metal sheet, and more particularly, to a continuous shearing apparatus preventing a thickness of a sheet from being increased during the process, decreasing a thickness deviation of the sheet in a longitudinal direction, and performing a continuous shearing for a long sheet such as a coil.
2. Description of the Conventional Art
A continuous shearing apparatus as shown in FIG. 1, called as an equal channel angular rolling (ECAR) apparatus, includes a rolling device for supplying a metal sheet 20 to dies and deformation dies with an L-shaped passage causing shear deformation when a metal sheet is passing there through. The rolling device is composed of two rollers 10a and 10b, and the dies are composed of an upper die 30a and a lower die 30b. Screws 40a and 40b for controlling the gap of the dies are provided at a dies fixing wall 50.
A metal sheet 20 through the rollers 10a and 10b passes an inlet passage between A and B and is pushed to an exit (a passage after B), and the metal sheet receives shear-deformation. As the result of the shear deformation, the microstructure of the sheet becomes grain-refined so that the shear deformed sheet may have improved mechanical properties such as high strength, formability, etc.
However, in the conventional continuous shearing apparatus, when a sheet 20 goes from the rollers 10a, 10b to the shear deformation zone (B), compressive stress is generated by deformation resistance at the shear deformation zone. Such a compressive stress increases the thickness of the sheet which goes into the shear deformation zone. When the thickened sheet passes through the shear deformation zone, a larger resistance is caused thereby to increase the sheet thickness much more. Thus, as the shear deformation process continues, the sheet gets thicker. When the thickness of the sheet exceeds a limited gap of the dies exit (after B), the shear deformation processing cannot be performed any longer. Consequently, the conventional apparatus is not appropriate to the continuous processing for long sheets, such as coils.